Integrated chips are constructed using complex fabrication processes that form a plurality of different layers on top of one another. Many of the different layers are patterned using photolithography, a process by which a photoresist material is selectively exposed to electromagnetic radiation. For example, photolithography may be used to define back-end-of-the-line metallization layers that are formed on top of one another. To ensure that the metallization layers are formed with a good structural definition, the electromagnetic radiation must be properly focused. To properly focus electromagnetic radiation, a workpiece must be substantially planar to avoid depth of focus problems.
Chemical mechanical polishing (CMP) is a widely used process by which both chemical and mechanical forces are used to globally planarize a semiconductor workpiece. The planarization prepares the workpiece for the formation of a subsequent layer. A typical CMP system comprises a rotating platen covered by a polishing pad. A slurry distribution system is configured to provide a chemical mechanical polishing slurry to the polishing pad. A workpiece is then brought into contact with the pad, causing the rotating platen to planarize the workpiece.